Apparatus for tinning electrical circuit wires and the like

ABSTRACT

An apparatus for tinning electrical circuits wires with a solder layer of tin or a tin alloy in which the wire is fed through a solder bath of tinning metal with the wire emerging upwardly therefrom in a substantially vertical direction, the exit point of the wire from the bath being encircled by a non-metallic tubular member, for example of quartz or quartz glass, with the casing having its adjacent end immersed in the bath. The upper end of the member is closed by a non-metallic insert which is spaced above the surface of the bath and is provided with an orifice through which the wire passes, the space between the insert and the surface of the bath being adapted, in use, to receive an agent which will inhibit, i.e., dissolve or prevent the formation of tin oxide, for example, an inert gas or zinc chloride. The insert may be provided with a supply passageway for the inhibiting material and may be provided with an annular shaped flange which may be positioned concentrically with respect to the exiting wire and disposed below said supply passageway, whereby material, such as zinc chloride, may be received on said flange and distributed around the exiting point of the wire from the tinning metal.

United States Patent [191 Trattner et a1.

Aug. 6, 1974 1 1 APPARATUS FOR TINNING ELECTRICAL CIRCUIT WIRES AND THE LIKE [75] Inventors: Hermann Trattner; Hans Raab,

both of Munich, Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin & Munich, Germany [22] Filed: Feb. 12, 1973 [21] Appl. No.; 331,851

[30] Foreign Application Priority Data Feb. 18, 1972 Germany 2207719 [52] US. Cl. 118/58, 118/421 [51] Int. Cl. B05c 3/15 [58] Field of Search 118/419, 123, 420, 125, [18/63, 58,404,405; 117/113, 114 R, 114 A, 114 B, 1 14 C [56] References Cited UNITED STATES PATENTS 1,930,601 10/1933 Townsend 118/D1G. 22 2,237,315 4/1941 Reilly 117/115 X 2,341,450 2/1944 Knaus 118/405 2,914,423 ll/1959 Knapp 118/125 X. 3,060,054 10/1962 Russell et a1 118/405 X 3,082,119 3/1963 Harris 117/115 X 3,167,403 1/1965 Smith et a1 117/114 X 3,561,399 2/1971 Federman 118/405 X 3,565,677 2/1971 Dion et a1. 118/405 X 3,707,400 12/1972 Harvey et a1 117/114 C X Primary Examiner-Morris Kaplan Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT An apparatus for tinning electrical circuits wires with a solder layer of tin or a tin alloy in which the wire is fed through a solder bath of tinning metal with the wire emerging upwardly therefrom in a substantially vertical direction, the exit point of the wire from the bath being encircled by va non-metallic tubular member, for example of quartz or quartz glass, with the casing having its adjacent end immersed in the bath. The upper end of the member is closed by a nonmetallic insert which is spaced above the surface of the bath and is provided with an orifice through which the wire passes, the space between the insert and the surface of the bath being adapted, in use, to receive an agent which will inhibit, i.e., dissolve or prevent the formation of tin oxide, for example, an inert gas or zinc chloride. The insert may be provided with a supply passageway for the inhibiting material and may be provided with an annular shaped flange which may be positioned concentrically with respect to the exiting wire and disposed below said supply passageway, whereby material, such as zinc chloride, may be received on said flange and distributed around the exiting point of the wire from the tinning metal.

9 Claims, 2 Drawing Figures \exexeaxeiam APPARATUS FOR TINNING ELECTRICAL CIRCUIT WIRES AND THE LIKE BACKGROUND OF THE INVENTION The invention is directed to an apparatus for tinning electrical circuit wires, particularly copper wires, with a relatively thick layer or coating of tin or a tin alloy.

In the coating of metal ribbons and wires with tin or a tin alloy, by the passage by the ribbon or wire through a solder bath containing the molten metal, it is well known to make use of an agent (usually zinc chloride) which dissolves tin oxide, and which is therefor employed in an effort to prevent the formation of stannic oxide which would contaminate the coating layer.

It has further been proposed, connection with the coating of steel ribbons and wires with molten metals or alloys, in particular with coatings containing zinc, antimony, bismuth or the like, in conjunction with exit or squeeze rollers in the molten bath, to provide a casing around the ribbon or wire at its point of exit from the metal melt, which may contain an agent (usually zinc chloride) which dissolves the oxide of the molten metal, to which agent ammonium bromide has been added. In this way, the surface of the bath may be kept free from impurities so that the following squeeze rollers employed also remain free from impurities.

In another known device, the wire is moved substantially vertically upwards through a solder bath and thereafter through a member having an annular clearance with respect to the wire which determines the coating thickness. Such device has been found to be well suited to the thick-tinning or hot tin plating of a copper wire. However, it has a disadvantage that after a period of operation of the device, the solder layer tends to become irregular. There is formed at the point of exit of the wire from the tin bath a small cone of liquid tin, termed the exit cone which surrounds the wire and has concave conical surfaces. Such exit cone must not experience any disturbance during the passing of the wire at constant speed through the tin bath, as it is only by means of such cone that it is ultimately possible to achieve a really uniform tin coating on the surface of the wire.

Finally, attempts have heretofore been made to an inert gas to keep the surfaceof zinc and tin baths free of oxides.

However, with none of these known procedures in the so-called exit cone maintained in undisturbed condition (i.e., unaltered) while the wire is passing through the solder bath. Likewise, squeeze rollers cannot be employed in the coating of thin copper wires with a uniform tin layer, as irrespective of the fact the crosssectional profile of the wire would be altered by the load on the roller, a flash is produced on the coating layer which must be avoided at all costs.

BRIEF SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an apparatus for tinning electrical circuits wires with a solder layer of tin or a tin alloy in which a solder bath of the tinning metal is provided, through which the wire is fed, with the wire emerging upwardly from the bath in a substantially vertical direction. A non-metallic tubular member or casing which has its adjacent end immersed in the bath is constructed to surround the wire at its point of exit from the metallic bath. The upper part of the member is closed by a nonmetallic insert the lower inner end of which is spaced from the surface of the bath with the insert being provided with a passageway therein through which the exiting wire passes. The space between the insert and the surface of the bath, in use, is adapted to contain an agent which will dissolve or prevent the formation of tin oxide, i.e., an inhibiting agent. Conveniently, the insert may be provided with a passage connecting the space within the casing above the surface of the bath, with a reservoir containing such an inhibiting agent.

By use of apparatus constructed in accordance with the present invention, a uniform exit cone of solder surrounding the wire is obtained. A desired layer of thickness can then be regulated by suitable section of the speed of passage of the wire through the solder bath. In this manner the layer thickness can be effectively and controllably varied from a few microns up to few hundredths of a mm. To achieve this result, the operation of the apparatus should be such that the speed of wire movement, as well as the temperature of the solder bath, be, as far as possible, maintained constant. Zinc chloride forms a very effective inhibiting agent as it will dissolve tin oxide and, surprisingly, it has been determined that zinc chloride is particularly suitable as an agent for reducing the surface tension of tin at the surface of the solder bath. Consequently, by means thereof, the surface tension of the tin may be substantially reduced in the area of the exit point of the wire, resulting in the production of a highly uniform exit cone surrounding the wire. The dissolved oxide residues collecting in the neighborhood of the enclosed space can, if required, be mechanically removed after a predetermined time.

It is also possible, in order to produce a uniform surface tension and to prevent the formation of tin oxide, to supply an inert gas to the enclosed space above the exit point of the wire, whereby oxide formation at the surface of the solder bath and at the exit cone is counteracted. However, this solution has the disadvantage that inert gas may escape at the point of exit from the wire at the enclosed space so that such method is utilizable only if a greater or lesser degree of loss of inert gas is acceptable.

Advantageously, the insert may consist of a plug of synthetic resinous material, and the passage for the introduction of the inhibiting agent which dissolves or prevents the formation of tin oxide, is laterally offset or eccentric with respect to the guide passageway for the wire.

As the insert is heated by radiated heat from the solder bath, the inhibiting agent, also introduced through the insert, is likewise heated before it reaches the surface of the solder bath. The plug of synthetic resinous material also may be provided with a laterally extending flange adjacent its lower or inner end, facing the bath surface, with the upper face of the flange, i.e., the face remote from the tin bath, being disposed directly below the point at which the supply passage for the inhibiting agent enters the enclosed space, with such flange being suitably shaped to form a trough or channel. The inhibiting agent thus may collect in such chan nel and overflow the peripheral edge of the flange onto the surface of the tin bath and by utilizing an annular shaped flange, substantially concentric with the exit point of the wire, a very effective and uniform distribution of the inhibiting agent may be achieved in the area at and surrounding the point of exit of the wire from the solder bath.

However, instead of employing an inhibiting agent adapted to dissolve tin oxide, such as zinc chloride, an inert gas can be fed through the supply passage to the tin bath, and as the tubular casing extends into the tin bath, an excessive loss of inert gas is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like reference characters indicate like or corresponding parts:

FIG. 1 is a schematic sectional view through an embodiment of the invention; and

FIG. 2 is a similar view of a portion of a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, a solder bath 1 is provided, contained within a suitable receptacle, adapted to be heated by a controllable, electrical heating arrangement 2, with the copper wire 3 to be tinned, being guided around a feed roller 4 and guide rollers 5 to a tinning device, indicated generally by the numeral 6. The copper wire will have already been pretreated i.e., rendered metallically clean and coated with a suitable flux. The device 6 is operative to maintain the surface tension of the solder bath constant, particularly in the area 7 of the point of exit of the wire and to facilitate the formation of a uniform exit cone 7 thereat.

The device 6 comprises a tubular member or casing 8, preferably made of a transparent material such as quartz glass. The adjacent end of the member 8 is immersed in the solder bath to a depth of approximately 10 mm. while the upper end of the tubular member is closed by means of an insert 9, formed of synthetic resinous material, having therein a passageway 9 through which the wire may be conducted to the exterior. The insert 9 also has a supply passage 10, disposed in offset or eccentric relation with respect to the passageway 9', which supply passage terminates at its inner end in a flange 12 with the latter being disposed in spaced relation above the surface 11 of the solder bath, enclosed by the device 6.

As the outer peripheral edge 13 of the upper face 13 of the flange 12 is disposed above the corresponding inner peripheral edge of the face, a trough or channellike structure is formed in which ihibiting material discharged from the passageway 13 may accumulate. In the construction illustrated, the upper face 13 of the flange 12 is of annular configuration and substantially concentric with the passageway 9 through which the wire passes, whereby inhibiting material may be uniformly distributed completely therearound.

The inhibiting agent, in this case a tin oxide dissolving agent, preferably zinc chloride, is supplied from a reservoir 14 through a control unit 15, equipped with an electromagnetic metering valve (not shown), which unit feeds the oxide dissolving agent continuously or batchwise through a pipe 16 into the passage 10.

As the insert 9 is heated by radiated heat from the solder bath and thermal conduction through the tubular member 8, the oxide dissolving agent flowing from the line 16 to the passageway 10 will be preheated in the insert and in the neighborhood of the trough or channel formed by the upper face 13 of the flange 12 whereby such inhibiting agents will drip over the edge 13' thereof in the manner illustrated in FIG. 1, onto the surface 11 of the solder bath. As a result, the surface tension of tin bath is maintained relatively closely constant in the neighborhood of the exit area 7 of the wire 3. As the surface of the solder bath should be maintained motionless at all times, there may be provided in the device 6, either in the tubular member 8 or, preferably in the insert 9, a venting bore 22 through which vapors arising from the tin oxide dissolving agent can be unimpededly bled off.

The layer thickness of the tin coating is dependent to a great extent on the feed rate v of the wire and the thickness of such coating is usually held between 5 and 15 microns. The tinning device 6 maybe supported in operation position with respect to the solder bath by suitable means, for example a cross beam 17.

FIG. 2 illustrates a tinning device for a copper wire 3 in accordance with further features of the invention, in which the surface tension of the bath 1 is maintained constant by an inert gas supplied to the enclosed space within the device 6.

As in the construction illustrated in FIG. 1, the adjacent end of the tubular member 8 is immersed in the solder bath 1, thus enclosing the surface area or zone immediately surrounding the exit point 7' of the wire from the bath. Likewise, the insert 9 is provided with a feed passage 10 offset or eccentrically disposed with respect to the wire guide passageway 9'. However, in this construction, the passage 10 is employed for the introduction of an inert gas, such as nitrogen, into the enclosed space 18, which is substantially closed at the insert 9 disposed above the surface 11 of the solder bath. The inert gas may be supplied from a pressure cylinder 19 and after passing through a reducing valve 20 and pipe 21, discharged through the passage 10 into the space 18, the gas being so regulated, in terms of quantity and/or pressure, that the space 18 over the surface 11 of the solder bath will be at a pressure slightly above atmospheric, which thus serves to insure that no air will reach the bath surface through the wirefeed passage 9'. Merely a small quantity of inert gas will continuously escape through the narrow annular gap between the surface of the wire 3 and the wall of the nozzle passage 9, as the width of such annular gap is very small, not exceeding 0.2 mm.

As a result of the increased atmospheric pressure existing in the space 18, the surface 11 of the bath within the member 8, will be slightly lower than the external bath surface 11 surrounding such member. The latter is constructed of a non-metallic material preferably of quartz, and preferably is transparent so that it is possible to directly observe the tinning operation within the member 8.

Having thus described our invention it is obvious that although minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. An apparatus for tinning electrical circuit wires with a solder layer of tin or tin alloy, comprising a solder bath of tinning metal, means for feeding a wire through said bath, with the wire emerging upwardly therefrom in a substantially vertical direction, and a non-metallic tubular member having one end immersed in the bath and arranged to surround said wire at its point of exit from said bath, a non-metallic insert closing the upper part of said member with said insert spaced above the surface of the bath and having a passageway therein through which the exiting wire passes, the space between said insert and the surface of the bath being adapted in use to receive an agent which will inhibit the formation of tin oxide a second passageway extending through said insert and communicating a source of said agent with said space, and a flange extending radially from the insert end which is adjacent to the surface of said bath, the upper face of said flange being spaced from and beneath the end of said second passageway.

2. An apparatus according to claim 1, wherein the closure over said exit point of the wire from said bath, formed by said tubular member and said insert, is provided with a vent therein for discharge to the exterior of vapor produced from said agent.

3. An apparatus according to claim 2, wherein said vent is provided in said insert.

4. An apparatus according to claim 1, wherein said tubular member is constructed of quartz or quartz glass.

5. An apparatus according to claim 1, wherein said insert is in the form of a plug of synthetic resinous material.

6. An apparatus according to claim 1, wherein the upper face of said flange has an annular configuration and encircles the wire passageway in said insert.

7. An apparatus according to claim 6, wherein the upper face of said flange has its outer peripheral edge spaced above its inner peripheral edge to form an annular trough for the reception of said inhibiting material, whereby the same may be distributed around the exit point of said wire from the bath.

8. An apparatus according to claim 1, wherein said supply passage is connected to a source of inert gas.

9. An apparatus according to claim 1, wherein said supply passage is connected to a source of material comprising at least in part zinc chloride. 

1. An apparatus for tinning electrical circuit wires with a solder layer of tin or tin alloy, comprising a solder bath of tinning metal, means for feeding a wire through said bath, with the wire emerging upwardly therefrom in a substantially vertical direction, and a non-metallic tubular member having one end immersed in the bath and arranged to surround said wire at its point of exit from said bath, a non-metallic insert closing the upper part of said member with said insert spaced above the surface of the bath and having a passageway therein through which the exiting wire passes, the space betweEn said insert and the surface of the bath being adapted in use to receive an agent which will inhibit the formation of tin oxide a second passageway extending through said insert and communicating a source of said agent with said space, and a flange extending radially from the insert end which is adjacent to the surface of said bath, the upper face of said flange being spaced from and beneath the end of said second passageway.
 2. An apparatus according to claim 1, wherein the closure over said exit point of the wire from said bath, formed by said tubular member and said insert, is provided with a vent therein for discharge to the exterior of vapor produced from said agent.
 3. An apparatus according to claim 2, wherein said vent is provided in said insert.
 4. An apparatus according to claim 1, wherein said tubular member is constructed of quartz or quartz glass.
 5. An apparatus according to claim 1, wherein said insert is in the form of a plug of synthetic resinous material.
 6. An apparatus according to claim 1, wherein the upper face of said flange has an annular configuration and encircles the wire passageway in said insert.
 7. An apparatus according to claim 6, wherein the upper face of said flange has its outer peripheral edge spaced above its inner peripheral edge to form an annular trough for the reception of said inhibiting material, whereby the same may be distributed around the exit point of said wire from the bath.
 8. An apparatus according to claim 1, wherein said supply passage is connected to a source of inert gas.
 9. An apparatus according to claim 1, wherein said supply passage is connected to a source of material comprising at least in part zinc chloride. 